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Aug 20, 2010

In the 1960s America's NASA undertook the Surveyor programme, a series of robotic missions to land on the Moon for the purposes of science and technology development to support the Apollo program. The very first mission of the programme, Surveyor 1, successfully achieved a soft landing in an equatorial mare region of the Moon (Oceanus Procellarum). That was the very first American propulsive Lander on another planetary body and came just three years before the first human landing. In total six of the seven Surveyor missions successfully achieved soft-landings, which gave the United States a very solid technological basis for later propulsive landing missions to the Moon, Mars and Venus.

Surveyor 3 Spacecraft, Credit NASA

A large part of the success of the Surveyor programme can be attributed to the selection of a simple and reliable mission architecture that had a pragmatic and incremental approach to solving the most critical engineering challenges of the time, namely the closed-loop terminal descent guidance and control system, throttleable engines, and the radar systems required for determining the Lander’s altitude and velocity. The Surveyor missions were the first time that NASA tested such systems in the challenging thermal and radiation environment near the Moon.

Key features of the missions were the choice of wide flat landing areas, a two-stage design (the first stage using a solid motor for braking), and the use of a 'direct-descent' trajectory that did not enter Moon orbit before landing. The main advantages of this approach were the relatively simple design of the engines for the landing stage, and the fact that a complex precision landing system was not needed. In the years following Surveyor, NASA developed more advanced landing technologies building upon Surveyor's critical systems and components, as well as the lessons learned during the programme.